The use of quantum confinement effects to improve electronic device performance has been under extensive investigation for some time. Quantum dot transistors are one example of such devices. A quantum dot transistor includes one or more quantum dots. Here, the term “quantum dot” refers to structures having 3-D quantum confinement.
The device of U.S. Pat. No. 5,714,766 is an example of a quantum dot transistor. In this device, current flow in a channel between a source and a drain is controlled with both a gate and a quantum dot. The quantum dot is electrostatically coupled to the channel via Coulomb blockade. The threshold voltage (i.e., the gate voltage at which the channel becomes conductive) depends on the number of charges stored on the quantum dot.
Another example is provided by U.S. Pat. No. 7,105,874. In this device, a quantum dot can be formed in a channel between the source and drain of a transistor during device operation. More specifically, carriers can be trapped to form accumulation and inversion layers that provide energy barriers for quantum confinement, thereby effectively forming a quantum dot. The energy levels of the resulting quantum dot can be used to control current flow through the channel.